The studies proposed here are part of this laboratory's major interest in the problem of cellular membranes. We propose to study in detail the synthesis and degradation of red cell membrane proteins. Initial in vivo experiments will use anemic rabbits injected with radioactive amino acids to determine the relative rates of synthesis and degradation of individual red cell membrane peptides. Subsequently this will be expanded to include in vitro experiments with rabbit reticulocytes in which synthesis of individual membrane peptides and glycoproteins will be compared to that of hemoglobin. Two specific peptides will be further purified to determine accurately their relative rates of synthesis as a clue to the mechanism to membrane assembly. Attempts will be made to raise specific antisera to these peptides. Finally, protein synthesis will be studied using cell-free rabbit reticulocyte lysates. Newly synthesized membrane proteins will be separated and identified by means of the specific antisera. We feel that this last approach offers the best means of studying in vitro factors involved in the generation of membrane units from newly synthesized proteins and may also provide insight into the factors that lead certain proteins to be incorporated into a water-insoluble milieu.